How to make a full limitaion connection to mailserver?

Hi everyone,I'm new in checkpoint management. My mail server working behind the checkpoint is recently attacked many times by DoS. The POP3 service receives many connections at a time that makes all mail services suspended.I'd like to configure a protection at IPS to block any IP that will be accessing to my mail server with exceeding a connection limitation.Can anyone guide me how to configure the checkpoint?

TechExams.Net is not sponsored by, endorsed
by or affiliated with Cisco Systems, Inc. Cisco®, Cisco Systems®,
CCDA™, CCNA™, CCDP™, CCNP™, CCIE™, CCSI™;
the Cisco Systems logo and the CCIE logo are trademarks or registered
trademarks of Cisco Systems, Inc. in the United States and certain other
countries. All other trademarks, including those of Microsoft, CompTIA, Juniper ISC(2),
and CWNP are trademarks of their respective owners.